Investment Securities (Amortized Cost And Fair Value Of Securities) (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
Jun. 30, 2015	Sep. 30, 2014
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	$ 174,509	$ 178,517
Available-for-Sale, Gross Unrealized Gains	6,307	6,871
Available-for-Sale Gross Unrealized Losses	729	691
Available-for-sale, Fair Value	180,087	184,697
Held-to-Maturity, Amortized Cost	4,941	5,419
Held-to-Maturity, Gross Unrealized Gains	544	430
Held-to-Maturity, Gross Unrealized Losses	0	0
Held-to-Maturity, Fair Value	5,485	5,849
Agency bonds and notes
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	7,573	12,269
Available-for-Sale, Gross Unrealized Gains	8	12
Available-for-Sale Gross Unrealized Losses	62	190
Available-for-sale, Fair Value	7,519	12,091
Agency-mortgage backed
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	48,137	51,845
Available-for-Sale, Gross Unrealized Gains	739	518
Available-for-Sale Gross Unrealized Losses	75	108
Available-for-sale, Fair Value	48,801	52,255
Held-to-Maturity, Amortized Cost	357	455
Held-to-Maturity, Gross Unrealized Gains	34	37
Held-to-Maturity, Gross Unrealized Losses	0	0
Held-to-Maturity, Fair Value	391	492
Agency CMO
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	21,431	29,648
Available-for-Sale, Gross Unrealized Gains	98	95
Available-for-Sale Gross Unrealized Losses	85	259
Available-for-sale, Fair Value	21,444	29,484
Privately-issued CMO
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	3,104	3,302
Available-for-Sale, Gross Unrealized Gains	495	618
Available-for-Sale Gross Unrealized Losses	0	0
Available-for-sale, Fair Value	3,599	3,920
Privately-Issued ABS
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	4,994	5,552
Available-for-Sale, Gross Unrealized Gains	1,448	1,801
Available-for-Sale Gross Unrealized Losses	0	0
Available-for-sale, Fair Value	6,442	7,353
SBA certificates
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	1,545	1,753
Available-for-Sale, Gross Unrealized Gains	13	9
Available-for-Sale Gross Unrealized Losses	0	0
Available-for-sale, Fair Value	1,558	1,762
Held-to-Maturity, Amortized Cost	0
Held-to-Maturity, Fair Value	0
Municipal obligations
Schedule of Cost-method Investments [Line Items]
Available-for-Sale, Amortized Cost	87,725	74,148
Available-for-Sale, Gross Unrealized Gains	3,506	3,818
Available-for-Sale Gross Unrealized Losses	507	134
Available-for-sale, Fair Value	90,724	77,832
Held-to-Maturity, Amortized Cost	4,584	4,964
Held-to-Maturity, Gross Unrealized Gains	510	393
Held-to-Maturity, Gross Unrealized Losses	0	0
Held-to-Maturity, Fair Value	$ 5,094	$ 5,357

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.2)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAmortizedCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of equity securities categorized neither as held-to-maturity nor as trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=49167202&loc=d3e26610-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 320

-Section 50

-Paragraph 2

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6957658&loc=d3e62557-112803

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesEquitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unrealized gain before deducting unrealized loss on investments in debt and equity securities classified as available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of unrealized loss before deducting unrealized gain on investments in available-for-sale securities.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27161-111563

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesGrossUnrealizedLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 25

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=51813488&loc=d3e22054-111558

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-03.1)

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.6)

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_HeldToMaturitySecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Fair value of investments in debt securities classified as held-to-maturity.

+ References

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of unrecognized gain before loss on investments in held-to-maturity securities.

+ References

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesUnrecognizedHoldingGains
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of unrecognized loss before gain on investments in held-to-maturity securities. Excludes write-down for other than temporary impairment (OTTI).

+ References

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesUnrecognizedHoldingLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfCostMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_AgencyBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_AgencyMortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_AgencyCollateralizedMortgageObligationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_CollateralizedMortgageObligationsIssuedByPrivateEnterpriseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_PrivatelyIssuedAbsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_SbaCertificatesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InvestmentTypeAxis=fsfg_UnitedStatesGovernmentAgenciesDebtSecuritiesAndMunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: